Janux Therapeutics, Inc. announced interim Phase 1 clinical data for PSMA-TRACTr JANX007 in adult subjects with metastatic castration-resistant prostate cancer (mCRPC) and provided a pipeline update. The data from eight patients from the first three cohorts of the dose escalation portion of the Phase 1a clinical trial, as of June 28, 2023 show that JANX007 has been generally well tolerated, with no dose-limiting toxicities. JANX007 has been dosed at 300µg flat dose, which is above the projected maximum tolerable dose of the parental T cell engagers.

JANX007 showed clinical activity at both 100µg and 300µg flat doses and yielded best overall PSA reductions between 31% and 67% in four of the five patients who received a flat dose. Grade 1 or 2 cytokine release syndrome (CRS) was observed only in patients who demonstrated PSA reductions, suggesting cytokine release resulting from anti-tumor activity was associated with CRS. No Grade 3 CRS has been observed.

The most common, non-CRS related adverse event observations have been generally consistent with tumor-specific activity and reduced PSMA(+) healthy tissue activity. No transaminitis was observed. JANX007 clinical development has moved into step-dosing and dose optimization with the goal to enhance efficacy while maintaining suitable safety results.

The TRACTr technology is designed to create potent T cell engagers (TCEs) by tumor-specific activation via mask cleavage by tumor proteases. Plasma levels in patients exhibited prolonged TRACTr exposure, clear evidence of activation as measured by a specific cleavage fragment, and lack of accumulation of the active TCE in the blood. The lack of TCE accumulation shows consistency with TRACTr design principles and suggest that observed PSA reductions have been a result of tumor activation and not systemic TCE exposure.

Janux’s first clinical candidate, JANX007, is a TRACTr that targets PSMA and is being investigated in a Phase 1 clinical trial in adult subjects with metastatic castration-resistant prostate cancer (mCRPC). Janux’s second clinical candidate, JANX008, is a TRACTr that targets EGFR and is being studied in a Phase 1 clinical trial for the treatment of multiple solid cancers including colorectal cancer, squamous cell carcinoma of the head and neck, non-small cell lung cancer, and renal cell carcinoma. Janux’s TRACIr drug candidate, JANX009, is designed for targeting both the programmed death-ligand 1 (PD-L1) receptor as well as the costimulatory CD28 receptor on T cells and is being investigated in preclinical studies for the treatment of solid tumors.

Janux is also applying its proprietary technology to develop a TRACTr designed to target TROP2, a clinically validated anti-tumor target that is overexpressed in various cancer types, such as breast, lung, urothelial, endometrial, ovarian, prostate, pancreatic, gastric, colon, head and neck, and glioma. In addition to named programs, Janux is generating a number of unnamed TRACTr and TRACIr programs for potential future development. Janux is a clinical-stage biopharmaceutical company developing tumor-activated immunotherapies for cancer.

Janux’s proprietary technology enabled the development of two distinct bispecific platforms: Tumor Activated T Cell Engagers (TRACTr) and Tumor Activated Immunomodulators (TRACIr). The goal of both platforms is to provide cancer patients with safe and effective therapeutics that direct and guide their immune system to eradicate tumors while minimizing safety concerns. Janux is currently developing a broad pipeline of TRACTr and TRACIr therapeutics directed at several targets to treat solid tumors.

Janux has two TRACTr therapeutic candidates in clinical trials, the first targeting PSMA is in development for prostate cancer, and the second targeting EGFR is being developed for colorectal, lung, head and neck, and renal cancers.